Additional ideas about the design by contract RFC

I like the idea a lot, although I'm not so sure of the proposed syntax. I would make it less specific. Preconditions/Postconditions assertions are indeed useful but the functionality could be extended to regular checks as well by making the error user defined. Plus, I would prefer having named checks rather than having the expression repeated every time: it's great for reusability and signatures would be shorter (... they are very lengthy already). For instance: public function offsetGet(int{NonNegative} $offset){} function NonNegative(int $offset){ if($offset < 0) throw new WhateverError; } If one wants them to act like assertions could still write: function NonNegative(int $offset){ assert($offset >= 0); } Some blue sky thinking code is here: http://pastie.org/10355629 Although, I'm not sure whether the validation function should be a simple named function or a type: public function baz(Foo{MyChecker} $foo); interface MyChecker extends Validator{} class MyStrictChecker implements MyChecker{ function check($value){ if($value < 10) throw new MyException; } } class MyDevChecker implements MyChecker{ function check($value){ assert($value >= 10); } } That could be useful, I believe, but kind of makes "the contract" too abstract. What do you think? Forgive my poor english.